1. Field of the Invention
The present invention relates to a sheet-like material coating system in a sheet-fed offset printing press.
2. Description of the Related Art
A polymer-based banknote circulating abroad, called xe2x80x9ca plastic banknotexe2x80x9d, requires the addition of a treating step after printing, as compared with printing of a banknote based on ordinary paper. That is, coating is performed for the following purposes:
(1) Protection for making printed surfaces wear minimally (Sealer).
(2) Decreasing gloss, and providing a paper-like texture (Matt).
Furthermore, printing intended to prevent forgery, such as printing with ultraviolet luminescent ink (Black Light), is often carried out during this treating step. For these reasons, a machine specifically designed for coating is additionally provided in a process for production of xe2x80x9ca plastic banknotexe2x80x9d. The coating treatment is performed in the following order: (1) If desired, offset printing aimed for prevention of forgery, (2) application of a sealer, and (3) matting.
Generally, a banknote is printed on both sides, and thus requires double-sided coating. Conventional examples of a machine constituted for this purpose are shown in FIGS. 5 and 6. FIG. 5 shows a system composed of two machines arranged for performing printing and coating of a face side and a back side of a sheet separately, in two passes, each machine comprising a feeding unit 100, a first offset printing unit 101, a second offset printing unit 102, a first coating unit 103, a second coating unit 104, and a delivery unit 105 provided in this order along flow of the sheet. FIG. 6 shows a system for performing only coating of a face side and a back side of a sheet in one pass by use of an inverting cylinder 108, the system comprising a feeding unit 100, a first coating unit 103, a second coating unit 104, a first offset printing unit 101, a second offset printing unit 102, a third coating unit 106, a fourth coating unit 107, and a delivery unit 105 provided in this order along flow of the sheet, the inverting cylinder 108 being interposed between the second coating unit 104 and the first offset printing unit 101.
However, the former system posed the problems of requiring a floor space for installation of the two machines, and necessitating operations for transporting and inverting the sheet between the machines. The latter system occupied a smaller space than the former system, but involved the problem of having a larger entire length per machine, and carrying the risk of causing scratches or rubs during inversion of the sheet.
The present invention has been accomplished in view of the above-described problems. It is an object of the invention to provide a sheet-like material coating system which can perform coating of a face side and a back side of a sheet in one pass with a reduced space and without requiring inversion of the sheet.
To attain the above object, the present invention claims a sheet-like material coating system for receiving and transferring a sheet-like material, and coating the sheet-like material, including:
an upstream cylinder and a downstream cylinder arranged adjacently in a direction of transport of the sheet-like material;
a first coating unit for coating a face side or a back side of the sheet-like material on the upstream cylinder;
a first drying device for drying the face side or back side of the sheet-like material on the upstream cylinder after coating by the first coating unit;
a second coating unit for coating the back side or face side of the sheet-like material on the downstream cylinder; and
a second drying device for drying the back side or face side of the sheet-like material after coating by the second coating unit.
According to the foregoing constitution, the coated surface is dried by the first drying device immediately after coating, so that an impression cylinder is prevented from being stained upon intimate contact with the coated surface during coating of the reverse surface. Consequently, double-sided coating is completed in one pass, thereby achieving a saving in space. Moreover, the sheet-like material is not inverted, and thus no scratches or rubs occur.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.